Scope pattern anylyst needed

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  • plus2
    Junior Member
    • Nov 2009
    • 26

    #16
    This is a 93 Dakota 3.9L Electronic spark timing.

    Comment

    • David Green
      Senior Member
      • Oct 2009
      • 382

      #17
      Hi I have had a look at the engine, its a V6 with a distributor fitted into the rear of the V section. Are you sure the distributor even though having electronic control does not have centrifugal weights fitted under the base plate for ignition advance?

      David

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      • plus2
        Junior Member
        • Nov 2009
        • 26

        #18
        I'm positive, it has a cam sensor/pickup coil

        Comment

        • greasybob
          Senior Member
          • May 2008
          • 1590

          #19
          I first want to say I in no way consider myself an expert at wave form analysis, I'm just a guy who experiments and practices alot. Any time I check an electrical device with windings (motors, relays, solenoids, coils) I want to see what they look like from a voltage veiw(back probe) and amperage(current ramp with a low amp probe). That being said I would check the coil with just one channel turned on. If useing a back probe set it to about a 50 ms sweep and 100 volts and adjust it from there so you can see all six cylinders firing and compare, maybe trigger off an injector so you know whats what, to me what you provided almost looks like you had channel 3 inverted, not sure. If the cam crank sync was off or one of the signals lost you should be able to see that by graphing that on the scanner side so just concentrate on checking the ignition with the scope for now. The ignition module is part of the PCM so you want to make sure all your grounds are good by checking voltage drop. Also maybe disconnect the alternator. A resistance check of the coil may be useful but current ramping is prefered. good luck And report back with what you find.
          Attached Files

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          • plus2
            Junior Member
            • Nov 2009
            • 26

            #20
            Got it

            Got it, I first changed the crank sensor because the waveform didn't match any know good that I could find, but never changed when problem occured. New crank sensor no difference. So I then tried a second PCM and nailed it finally. I want to greatly thank everyone that helped. I've learned alot, how to take and post a snapshot and to keep a library of known good waveforms.

            Thank you

            Comment

            • hefaus
              Senior Member
              • Dec 2007
              • 435

              #21
              nailed it

              Originally posted by plus2
              Got it, I first changed the crank sensor because the waveform didn't match any know good that I could find, but never changed when problem occured. New crank sensor no difference. So I then tried a second PCM and nailed it finally. I want to greatly thank everyone that helped. I've learned alot, how to take and post a snapshot and to keep a library of known good waveforms.

              Thank you
              Hi Can you post a repaired waveform? Glad you figured it out.

              Comment

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